The document provides an overview of key considerations for evaluating lighting solutions, including luminaire classification, technical aspects, and functional aspects. It discusses luminaire illumination and how reflector shape, type, and material impact light quality and direction. Optical systems aim to meet desired illumination through properties like reflectance, shielding angles, and diffusion of light. Reflector size and material efficiency are also addressed in distributing light as intended.

1. Luminaires – An Overview:
Facts, Basics and Considerations
Target Audience:
Facility managers, Procurement managers,
Technical managers, Maintenance managers
and General Lighting enthusiasts
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2. Luminaire Overview – Objectives
The purpose of this outline is to provide an overview
and to familiarize the decision maker with the key
considerations when evaluating a lighting solution
Luminaire Overview Topics:
a. Luminaire classification
b. Luminaire technical aspects
c. Luminaire functional aspects
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3. Module 3
Luminaire Functional Aspects
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4. Luminaire – Illumination
The optical system of a given luminaire is paramount for
meeting the desired illumination. The reflector shape, type,
and material are key for light quality in matters of intensity and
direction.
This section will discuss the following:
Illumination basic terms
Photometrics, curves & distribution
Luminaires and Reflectors
efficiency and DLOR (Downward Light Output Ratio)
materials, type and reflection
louvers and light diffusion
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5. Illumination - Basics
The Inverse Square Law of light states that:
the power of the light on an object is inversely proportional to
the square of the distance (d) from the source …
E ~ /d²
E – illuminance intensity on a surface. measured in lux.
1m 2m
3m 4m
E= 100 lux E= 25 lux E= 11 lux E= 6 lux
(100/1²) (100/2²) (100/3²) (100/4²)
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6. Illumination – angle & intensity
Intensity measured at 180 pointing
towards the ceiling
Intensity at 150
Intensity at 90
Intensity values are in
cd/1000 lm (lumen)
Intensity at 30
cd – candela, luminous
Intensity measured at 0 pointing
intensity system unit towards the floor
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7. Photometric distribution –
polar intensity diagram
Polar luminous intensity graph: The diagram illustrates the distribution of
luminous intensity, in candelas, of the luminaire. The photometric curve
provides a visual guide to the type of light distribution produced by the
luminaire e.g. wide, narrow, direct, indirect etc.
150 180 150 The diagram shows
Intensity values in the illumination
cd/1000 lm against vertical and
120 120 horizontal angles of
the luminaire. For
90 90 example, the
100 luminous intensity
200
at 0˚ horizontal
60 60
300
angle and 30˚
400 vertical angle is
30 0 30 300cd.
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8. Photometric curve types and applications
The reflector has a key role in defining the light distribution pattern of a luminaire
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9. Photometrics and IES files
Luminaire photometrics is illustrated by an IES file
An IES file visually illustrates
several dimensions/rotation
Any quality luminaire would
come with an IES file which can
be viewed by a software
program rotating it.
Commonly used software is IES
viewer by
http://www.photometricviewer.com
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10. Reflector – Quality and Quantity Illumination
The reflector and the optical system of a given luminaire is
paramount for meeting the desired illumination. The reflector
shape and type, material are key for light quality in matters of
intensity and direction.
Direct
lamp light
Reflected
lamp light
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11. Reflectors & Lamp size: Efficiency & DLOR
T8 vs T5 Fluorescent
As a rule of thumb the smaller the lamp the more efficient the reflector would be.
DLOR – Downward Light Output Ratio
T8 fluorescent diameter is 8/12”, while T5 fluorescent diameter is of 5/12”.
The illustration clearly shows that T8 obstructs some of its own light.
It is estimated that 5%-10% of T8 light is being obstructed compared with
T5.
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12. Reflectors & Lamp Size: Efficiency & DLOR
Quartz MH vs. Ceramic MH
Quartz MH Ceramic MH
bulb: ~ 9”, 23 cm bulb: ~ 3”, 7 cm
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13. Reflector – Size matters
Smaller Reflector is considered more advantageous due to the
following arguments:
• Less material required, eg. cheaper BOM & cheaper logistics
• More efficient by design
• Higher precision of light orientation illumination
• Better quality materials are utilized, due to smaller size
• Smaller size design usually more architectural in nature
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14. Reflectors: Material, Type & Reflectance
Type Material Reflectance
Specular Commercial grade aluminum Up to 0.7
Aluminum with quality coating 0.8-0.9 (based on coating & color)
Glass or plastic w’ aluminum 0.85-0.89
coating
Multi coated polyester film 0.95-0.98
Spread Brushed aluminum 0.5-0.6
Peened aluminum 0.7-0.8
Diffuse White pain on steel ~ 0.8 (up to)
Glossy white plastic ~ 0.9 (up to)
Specular Spread Diffuse
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15. Luminaire – light shielding qualities
Among luminaire qualities is light shielding. Improved light screening with low
cut design is a desirable attribute for a luminaire .
Shielding Angle : an angle beyond which light is not visible
Cut off Angle : 90 -shielding angle
Low cut profile
Cut off angle
Shielding angle Shielding angle
Luminaire A Luminaire B
Luminaire “B”, has same cut off angle as “A”,
while having low cut profile
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16. Luminaire – light reflection & diffusing
Luminaire louvers facilitate light reflection and diffusion aiming
to provide pleasant and quality light spread.
Ray of light at angle
less than shielding
angle is diffusely
reflected
Shielding angle
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17. Luminaire – parabolic reflectors & diffusing
Luminaires with parabolic louvers enable orientation and
diffusion of light along desired direction.
Shielding angle
Reflected light rays
are oriented along
desired direction
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18. The End
Luminaires by Light-Ref.com
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